Until recently, only the iPhone has featured a camera in all of the available models. However the latest generation of both the iPod touch and iPad now also have cameras.

The original iPhone and iPhone 3G feature a fixed-focus 2.0-megapixel camera, while the iPhone 3GS features a 3.2-megapixel camera with auto-focus, auto-white balance and auto-macro focus (up to 10cm). The iPhone 3GS camera is also able of capturing 640×480 pixel video at 30 frames per second. Although the earlier models are physically capable of capturing video, they are limited in software and this feature is not available at the user level. The latest iPhone 4 features a 5-megapixel camera with better low-light sensitivity and backside illuminated sensor. The camera has an LED flash and is capable of capturing 720p HD video at 30 frames per second. The iPhone 4 also has a lower-resolution front-facing camera, which is capable of capturing 360p HD video at 30 frames per second.

The latest generation of iPod touch and iPad also have both rear- and front-facing cameras, both of which are far lower resolution than the camera fitted to the iPhone 4, see Table 2-1 for details. You’ll notice the difference in sizes between still and video images on the iPod touch and the iPad 2. It’s unclear whether Apple is using a 1280×720 sensor and cropping off the left and right sides of the video image for still images, or whether it is using a 960×720 sensor and up-scaling it on the sides for video. The later would be an unusual approach for Apple, but is not inconceivable.

All models produce geocoded images by default.

The UIImagePickerViewController is an Apple-supplied interface for choosing images and movies, and taking new images or movies (on supported devices). This class handles all of the required interaction with the user and is very simple to use. All you need to do is tell it to start, then dismiss it after the user selects an image or movie.

Let’s go ahead and build a simple application to illustrate how to use the image picker controller. Open Xcode and start a new project. Select a View-based Application for the iPhone, and name it Media when requested.

The first thing to do is set up the main view. This is going to consist of a single button that is pressed to bring up the Image Picker controller. An UIImageView will display the image, or thumbnail of the video, that is captured.

Select the MediaViewController.h interface file to open it in the editor and add a UIButton and an associated method to the interface file. Flag these as an IBOutletand IBAction respectively. You also need to add a UIImageView to display that image returned by the image picker, which also needs to be flagged as an IBOutlet. Finally, add a UIImagePickerController, and flag the view controller as both UIImagePickerControllerDelegate and UINavigationControllerDelegate. The code to add to the default template is shown in bold:

#import <UIKit/UIKit.h>

@interface MediaViewController : UIViewController
      <UIImagePickerControllerDelegate, UINavigationControllerDelegate> {

    IBOutlet UIButton *pickButton;
    IBOutlet UIImageView *imageView;
    UIImagePickerController *pickerController;
}

-(IBAction) pickImage:(id) sender;

@end

Next, open the MediaViewController.m implementation file and add a stub for the pickImage: method. As always, remember to release the pickButton, imageView and the pickerController in the dealloc method:

-(IBAction) pickImage:(id) sender {
    // Code goes here later
}

- (void)dealloc {
    [pickButton release];
    [imageView release];
    [pickerController release];
    [super dealloc];
}

After saving your changes (⌘-S) single click on the MediaViewController.xib NIB file to open it in Interface Builder. Drag and drop a UIButton and a UIImageView into the main View window. Go ahead and change the button text to something appropriate, and in the Attributes Inspector of the Utilities panel set the UIImageView’s view mode to be Aspect Fit. Use the Size inspector resize the UIImageView to a 4:3 ratio. I used 280×210 points which fits nicely in a Portrait-mode iPhone screen.

Next click on “File’s Owner” in the main panel. In the Connections inspector of the Utilities panel, connect both the pickButton outlet and the pickImage: received action to the button you just dropped into the View choosing Touch Up Inside as the action, see Figure 2-1.

Figure 2-1. Connecting the UIButton to File’s Owner

Then connect the imageView outlet to the UIImageView in our user interface.

Click on the MediaViewController.m implementation file and uncomment the viewDidLoad: method. You’re going to use this to initialize the UIImagePickerController. Make the changes shown in bold:

- (void)viewDidLoad {
    [super viewDidLoad];
    pickerController = [[UIImagePickerController alloc] init];
    pickerController.allowsEditing = NO;
    pickerController.delegate = self;
}

The UIImagePickerController can be directed to select an image (or video) from three image sources: UIImagePickerControllerSourceTypeCamera, UIImagePickerControllerSourceTypePhotoLibrary and UIImagePickerControllerSourceTypeSavedPhotosAlbum. Each presents a different view to the user allowing her to take an image (or a video) with the camera, from the image library, or from the saved photo album.

Now write the pickImage: method that will present the image picker controller to the user. There are a few good ways to do that, depending on the interface you want to present. The first method, makes use of a UIActionSheet to choose the source type, presenting the user with a list to decide whether they will take a still image or a video:

-(void)pickImage: (id)sender {
    UIActionSheet *popupQuery = [[UIActionSheet alloc]
        initWithTitle:nil
        delegate:self
        cancelButtonTitle:@"Cancel"
        destructiveButtonTitle:nil
        otherButtonTitles:@"Photo",@"Video",nil];

    popupQuery.actionSheetStyle = UIActionSheetStyleBlackOpaque;
    [popupQuery showInView:self.view];
    [popupQuery release];
}

If we’re going to use this method we must specify that the view controller supports the UIActionSheetDelegate protocol in the interface file:

@interface MediaViewController : UIViewController 
  <UIImagePickerControllerDelegate, UINavigationControllerDelegate,
  UIActionSheetDelegate> {

In the implementation file, provide an actionSheet:clickedButtonAtIndex: delegate method to handle presenting the image picker interface. If there is no camera present the source will be set to the saved photos album:

- (void)actionSheet:(UIActionSheet *)actionSheet 
      clickedButtonAtIndex:(NSInteger)buttonIndex {
      
    if ([UIImagePickerController
         isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {

       pickerController.sourceType = UIImagePickerControllerSourceTypeCamera;
    } else {
       pickerController.sourceType =
        UIImagePickerControllerSourceTypeSavedPhotosAlbum;
    }

    if (buttonIndex == 0) {
        pickerController.mediaTypes = [NSArray arrayWithObject: kUTTypeImage];
    } else if (buttonIndex == 1) {
        pickerController.mediaTypes = [NSArray arrayWithObject: kUTTypeMovie];
    }
    [self presentModalViewController:pickerController animated:YES];
}

Since we’ve made use of the kUTTypeImage and kUTTypeMovie type codes in this method we have to add the Mobile Core Services framework to our project.

To add the framework, select the Media project file in the Project navigator window. You should see a panel as in see Figure 2-2. Select the Target and click on the Build Phases tab. Select the Link with Libraries drop down and use the + button to add the MobileCoreServices.framework from the list of available frameworks.

Add the following to the view controller interface file:

#import <MobileCoreServices/MobileCoreServices.h>

After saving the changes you can click on the Build and Run button. You should be presented with an interface much like Figure 2-3 (left). Clicking on the “Go” button you should be presented with the UIActionSheet that prompts the user to choose between still image and video capture.

Instead of explicitly choosing an image or video via the action sheet, you could instead allow the user to pick the source. The following alternative code determines whether your device supports a camera and adds all of the available media types to an array. If there is no camera present the source will again be set to the saved photos album:

-(void)pickImage: (id)sender {
   if ([UIImagePickerController
         isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
      pickerController.sourceType = UIImagePickerControllerSourceTypeCamera;
      NSArray* mediaTypes =
        [UIImagePickerController availableMediaTypesForSourceType:
                              UIImagePickerControllerSourceTypeCamera];
      pickerController.mediaTypes = mediaTypes;
   } else {
      pickerController.sourceType =
        UIImagePickerControllerSourceTypeSavedPhotosAlbum;
   }
   [self presentModalViewController:pickerController animated:YES];
}

Figure 2-2. Adding the MobileCoreServices.framework to the project

Here instead of presenting an action sheet and allowing the user to choose which source type they wish to use we interrogate the hardware and decide which source types are available. We can see the different interfaces these two methods generate in Figure 2-4. The left interface is the still camera interface, the middle image is the video camera interface and the final (right-hand) image is the joint interface, which allows the user to either take still image or video.

Figure 2-3. The initial Media application interface (left), the UIActionSheet that pops up when the button is pressed (middle), and the Saved Photos folder that appears when the camera is unavailable (right)

Figure 2-4. The three different UIImagePickerController interfaces

The final interface, where the user may choose to return either a still image or a video, is the one presented by the second version of the pickImage: method. This code is also more flexible as it will run unmodified on any of the iPhone models that have a camera device. If your application requires either a still image or a video (and can not handle both) you should be careful to specify either kUTTypeImage or kUTTypeMovie media type as you did in the first version of the method.

You can choose either of the two different methods I’ve talked about above to present the image picker controller to the user. In either case when the user has finished picking an image (or video) the following delegate method will be called in the view controller:

-(void)imagePickerController:(UIImagePickerController *)picker 
      didFinishPickingMediaWithInfo:(NSDictionary *)info {
      
   if( [info objectForKey:@"UIImagePickerControllerMediaType"] == 
       kUTTypeMovie ) {

      // add code here

   } else {
      imageView.image = 
        [info objectForKey:@"UIImagePickerControllerOriginalImage"];

   }
   [self dismissModalViewControllerAnimated:YES];
}

When the UIImagePickerController returns it passes an NSDictionary containing a number of keys, listed in Table 2-2. Use the UIImagePickerControllerMediaType key to decide whether the image picker is returning a still image or a movie to its delegate method.

We can retrieve the original image (or cropped version if editing is enabled) directly from the NSDictionary that was passed into the delegate method. This image reference can be passed directly to the UIImageView and displayed, as shown in the code in the next section and Figure 2-5.

Figure 2-5. A thumbnail of a single frame of video displayed in a UIImageView

There is no easy way to retrieve a thumbnail of a video, unlike still photos. This section illustrates two methods of grabbing raw image data from an image picker.

-(void)imagePickerController:(UIImagePickerController *)picker 
      didFinishPickingMediaWithInfo:(NSDictionary *)info {
      
    if( [info objectForKey:@"UIImagePickerControllerMediaType"] ==
        kUTTypeMovie ) {
        CGSize pickerSize = CGSizeMake(picker.view.bounds.size.width,
                                       picker.view.bounds.size.height-100);
        UIGraphicsBeginImageContext(pickerSize);
        [picker.view.layer renderInContext:UIGraphicsGetCurrentContext()];
        UIImage *thumbnail = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        imageView.image = thumbnail;

    } else {
          imageView.image = image;

    }
    [self dismissModalViewControllerAnimated:YES];
}

#import <QuartzCore/QuartzCore.h>

-(void)imagePickerController:(UIImagePickerController *)picker 
      didFinishPickingMediaWithInfo:(NSDictionary *)info {
      
    if( [info objectForKey:@"UIImagePickerControllerMediaType"] ==
        kUTTypeMovie ) {

        AVURLAsset *asset=[[AVURLAsset alloc]
           initWithURL:[info objectForKey:UIImagePickerControllerMediaURL]
                                  options:nil];
        AVAssetImageGenerator *generator =
           [[AVAssetImageGenerator alloc] initWithAsset:asset];
        generator.appliesPreferredTrackTransform=TRUE;
        [asset release];
        CMTime thumbTime = CMTimeMakeWithSeconds(0,30);

        AVAssetImageGeneratorCompletionHandler handler =
               ^(CMTime requestedTime, CGImageRef im, CMTime actualTime,
                 AVAssetImageGeneratorResult result, NSError *error) {
            if (result != AVAssetImageGeneratorSucceeded) {
                NSLog(@"Error:%@", error);
            }
            imageView.image = [[UIImage imageWithCGImage:im] retain];
            [generator release];
        };

        CGSize maxSize = CGSizeMake(320, 180);
        generator.maximumSize = maxSize;
        [generator generateCGImagesAsynchronouslyForTimes:
            [NSArray arrayWithObject:[NSValue valueWithCMTime:thumbTime]]
                   completionHandler:handler];

    } else {
          imageView.image = image;

    }
    [self dismissModalViewControllerAnimated:YES];
}

#import <AVFoundation/AVFoundation.h>
#import <CoreMedia/CoreMedia.h>

You can save both images and videos to the Photo Album using the UIImageWriteToSavedPhotosAlbum and UISaveVideoAtPathToSavedPhotosAlbum methods. The method will also obtain a thumbnail image for the video if desired.

The saving functions in this example are asynchronous; if the application is interrupted (e.g., takes a phone call) or terminated, the image or video will be lost. You need to ensure that your user is aware that processing is happening in the background as part of your application interface.

The following example save the image to the Photo Album by adding a call to UIImageWriteToSavedPhotosAlbum to the image picker delegate. The example will then provide feedback when the image has been successfully saved or an error occurs. Add the following highlighted lines to the image picker controller presented earlier in the chapter:

-(void)imagePickerController:(UIImagePickerController *)picker 
      didFinishPickingMediaWithInfo:(NSDictionary *)info {
      
   if( [info objectForKey:@"UIImagePickerControllerMediaType"] == 
       kUTTypeMovie ) {
       
        CGSize pickerSize = CGSizeMake(picker.view.bounds.size.width,
                                       picker.view.bounds.size.height-100);
        UIGraphicsBeginImageContext(pickerSize);
        [picker.view.layer renderInContext:UIGraphicsGetCurrentContext()];
        UIImage *thumbnail = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        imageView.image = thumbnail;

   } else {
       UIImage *image =
          [info objectForKey:@"UIImagePickerControllerOriginalImage"];
       UIImageWriteToSavedPhotosAlbum(
           image,
           self,
           @selector(
             imageSavedToPhotosAlbum:didFinishSavingWithError:contextInfo:),
           nil);

       imageView.image = image;
   }
   [self dismissModalViewControllerAnimated:YES];
}

Then add the following method, which presents a UIAlertView notifying the user that the save has occurred:

- (void)imageSavedToPhotosAlbum:(UIImage *)image 
      didFinishSavingWithError:(NSError *)error 
      contextInfo:(void *)contextInfo {

    NSString *title;
    NSString *message;
    if (!error) {
        title = @"Photo Saved";
        message = @"The photo has been saved to your Photo Album";
    } else {
        title = NSLocalizedString(@"Error Saving Photo", @"");
        message = [error description];
    }
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title 
                                                    message:message 
                                                   delegate:nil 
                                          cancelButtonTitle:@"OK" 
                                          otherButtonTitles:nil];
    [alert show];
    [alert release];
}

You can similarly add the following highlighted lines to the delegate method to save captured video:

-(void)imagePickerController:(UIImagePickerController *)picker
      didFinishPickingMediaWithInfo:(NSDictionary *)info {

   if( [info objectForKey:@"UIImagePickerControllerMediaType"] == kUTTypeMovie ) {
       NSString *tempFilePath =
          [[info objectForKey:UIImagePickerControllerMediaURL] path];
       if ( UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(tempFilePath) ) {
         UISaveVideoAtPathToSavedPhotosAlbum( tempFilePath, self,
            @selector(video:didFinishSavingWithError:contextInfo:),
            tempFilePath);
       }

        CGSize pickerSize = CGSizeMake(picker.view.bounds.size.width, 
                                       picker.view.bounds.size.height-100);
        UIGraphicsBeginImageContext(pickerSize);
        [picker.view.layer renderInContext:UIGraphicsGetCurrentContext()];
        UIImage *thumbnail = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        imageView.image = thumbnail;

   } else {
       UIImage *image = 
         [info objectForKey:@"UIImagePickerControllerOriginalImage"];
       UIImageWriteToSavedPhotosAlbum(image, self,
         @selector(
          imageSavedToPhotosAlbum:didFinishSavingWithError:contextInfo:), nil);

       imageView.image = image;
   }
   [self dismissModalViewControllerAnimated:YES];
}

Next add the following method to report whether the video has been successfully saved to the device’s Photo Album, or an error occurred:

- (void)video:(NSString *)videoPath 
       didFinishSavingWithError:(NSError *)error 
       contextInfo:(NSString *)contextInfo {

    NSString *title;
    NSString *message;
    if (!error) {
        title = @"Video Saved";
        message = @"The video has been saved to your Photo Album";
    } else {
        title = NSLocalizedString(@"Error Saving Video", @"");
        message = [error description];
    }
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title 
                                                    message:message 
                                                   delegate:nil 
                                          cancelButtonTitle:@"OK" 
                                          otherButtonTitles:nil];
    [alert show];
    [alert release];
}

Make sure you’ve saved your changes, and click on the Run button in the Xcode toolbar to compile and deploy the application to your device. If everything is working, you will see a thumbnail after you take a photo or video. After a few seconds a confirmation dialog will appear reporting success or an error. See Figure 2-6.

Figure 2-6. Saving images (or video) to the Photo Album

If you are capturing video you can make some video-specific customizations using the videoQuality and videoMaximumDuration properties of the UIImagePickerController class:

pickerController.videoQuality = UIImagePickerControllerQualityTypeLow;
pickerController.videoMaximumDuration = 90; // Maximum 90 seconds duration

Table 2-3 illustrates the expected sizes of a typical 90 second movie file for the three possible image quality levels, which defaults to UIImagePickerControllerQualityTypeMedium.

The maximum, and default, value for the videoMaximumDuration property is 10 minutes. Users are forced to trim longer video to match the duration you request.